Composite shaft with outer periphery ring

ABSTRACT

A drive shaft has a central tubular portion formed of a polymer composite with imbedded fibers. It extends between a first end and a second end. The central tubular portion has an outer peripheral surface. There is at least one ring on the outer peripheral surface of the central tubular portion. A method of repairing a composite material tube includes the steps of (a) identifying a damaged area on a composite tube, and (b) placing a patch on a surface of the tube and over the damaged area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/247,966 filed Jan. 15, 2019.

BACKGROUND

This application relates to composite drive shafts and methods ofrepair.

Drive shafts are utilized in any number of modern industrialapplications. As one example, drive shafts are utilized to drivecomponents in an aerospace environment. One specific application mightbe driving propellers associated with a helicopter, as an example.

Drive shafts might have some bending flexure along the length duringoperation. Thus, it is known to position dampers or other structuresalong the length of the drive shaft to limit this bending deflection.The dampers are often associated with a “rub ring” which is an elementextending radially outwardly of the drive shaft to contact the damperand protect, therefore, the outer surface of the shaft in case ofcontact with the damper.

Historically, drive shafts were formed of metal and, in particular,often aluminum, titanium or steel. More recently, it has been proposedto provide drive shafts formed of composite materials.

Drive shafts may also become damaged. They are often replaced oncedamaged instead of being repaired.

SUMMARY

A drive shaft has a central tubular portion formed of a polymercomposite with imbedded fibers. It extends between a first end and asecond end. The central tubular portion has an outer peripheral surface.There is at least one ring on the outer peripheral surface of thecentral tubular portion.

A method of repairing a composite material tube includes the steps of(a) identifying a damaged area on a composite tube, and (b) placing apatch on a surface of the tube and over the damaged area.

These and other features may be best understood from the followingdrawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a side view of a drive shaft schematically driving acomponent.

FIG. 1B schematically shows a detail of a rub ring in a diametriccross-sectional view.

FIG. 2A shows a diametric cross-section of a first embodiment of a rubring.

FIG. 2B shows a diametric cross-section of a second embodiment of a rubring.

FIG. 2C shows a diametric cross-section of a third embodiment of a rubring.

FIG. 3A shows a damaged drive shaft.

FIG. 3B is an axial cross-section through the damaged drive shaft.

FIG. 4A shows an axial cross-sectional view of a repair step.

FIG. 4B shows an axial cross-sectional view of an optional second repairstep.

FIG. 4C is a diametric cross-section through the FIG. 4B drive shaft.

DETAILED DESCRIPTION

FIG. 1A shows a drive system 18 having a drive shaft 20. Drive shaft 20may have a central composite tubular portion 30 connecting two metallicflanges 26 and 28 at ends 17 of the central tubular portion 30. Theflanges may be riveted such as shown at 27 or connected with the shaft20 by other fasteners. A drive input 22 drives the shaft 20 to, in turn,drive the drive output 24. The output 24 may be an aerospace componentand, in one example a propeller on a helicopter. While metallic flanges26/28 are illustrated, the flange could be composite. In fact, thetubular portion could be used without end flanges at all.

Rub rings 32 are shown on an outer peripheral surface 19 of the centraltubular portion 30. The rub rings 32 are axially aligned with staticcomponents such as a damper 34. During operation, there may be flexingalong the length of the central tubular portion 30 and the rub rings 32may contact the damper 34 to limit that flexing.

FIG. 1B shows a detail with regard to the rub rings 32 and the centraltubular portion 30. A first radius R₁ may be defined from a center C ofthe composite tubular portion 30 to an outer peripheral surface 31 ofthe composite tubular portion 30. A second radius R₂ may be defined fromthe center C to an outer peripheral surface 33 of the rub ring 32. Aratio of R₂ to R₁ is greater than or equal to 1.01 and less than orequal to 1.50. In further embodiments, the ratio is less than or equalto 1.25.

The central tubular portion 30 is formed of a fiber-reinforcedthermoplastic material. The components of the central tubular portionand the rings may be formed of the same or different fiber-reinforcedpolymer matrix composite materials. In one embodiment, the matrix can bea thermoplastic polymer. In another embodiment, the matrix 100 can be athermoset polymer. Different types of reinforcing fibers 101, such as,for example, carbon fibers, glass fibers, organic fibers, or theircombinations can be used in different embodiments. In differentembodiments, the same or different fabrication processes, such as forexample, automated fiber placement, filament winding, braiding,wrapping, etc. can be used to make separate composite tubes, flangesand, if applicable, diaphragms.

FIG. 2A shows a first embodiment 40 wherein the shaft inner tube portion42 is provided with the ring 44. Ring 44 may be formed of the samegeneral material as the tube 42. On the other hand, there may be somedifference in composition, such as fiber type, fiber volume fractionpercentage, fiber arrangement, polymer matrix type, etc. dependent onthe operational needs for the particular location on that shaft.

In embodiments, the ring could be formed of polymer material, with, orwithout, embedded fibers.

When central tubular portion 42 and ring 44 are formed of the samematerial, they may be bonded together during formation.

FIG. 2B shows an embodiment 46, where the central tubular portion 42 isattached to a ring 50 through an adhesive 48.

The ring 50 in the embodiment 46 may be formed of a different materialthan the central tubular portion 42. Ring 50 might be a distinctthermoplastic, a thermoset, or even a metallic component. Here too thesame material may be used.

FIG. 2C shows yet another embodiment 52. Here, the central tubularportion 42 is provided with a ring 56 through an optional adhesive layer54. Ring 56 and central tubular portion 42 might actually be similar toeither embodiment 40 or 46. However, an outer elastomer ring 60 isprovided with a bond layer 58 to the outer periphery of the ring 56.This elastomer ring at layer 60 can provide further cushioning duringcontact between the rub ring and a static component such as a damper 34.

In other embodiments, layer 60 is not limited to elastomers. This layer60 may be of a low friction material, such as for example Teflon, toprovide efficient interaction with damping ring 34. Layer 60 could begenerically called a cushioning member.

A drive shaft according to this disclosure could be said as having acentral tubular portion formed of a thermoset resin with imbeddedfibers, and extending between a first end and a second end. The centertubular portion has an outer peripheral surface and there is at leastone ring on the outer peripheral surface of the central tubular portion.

FIG. 3A shows another feature directed to repairing a damaged driveshaft 80. Here, damage 82 is shown. Damage 82 can be seen in an axialcross-section in FIG. 3B as a hole extending through an entire thicknessof the tubular portion 80. However, it should be understood that thedamage 82 need not extend through the entire thickness, and could be atleast partial one at an inner or/and outer surface of the tube.

FIG. 4A shows a an axial cross-section with a first step in repairingthe tubular portion 90 by utilizing one or more patches 92A, 92B, 92C.The patches may be similar in composition to the drive shaft materials.In other embodiments the materials of patches may be of differentpolymer matrices reinforced with different fibers, such as carbon,glass, organic fibers or their combinations, or have no fiberreinforcement at all. The patches need not extend around the entirecircumference of the tubular portion, but may only be at a limitedcircumferential area.

FIG. 4B shows an axial cross-section with an optional feature wherein asecond patch area 96 is provided to balance any radial misalignment thatthe first patch area 92 might have caused. The two patches 92 and 96 canbe seen to be circumferentially spaced, but axially aligned. Thelocation of patch 92 is selected to provide balancing of the tubularportion. Thus, a repaired tube or shaft 94 is shown in FIG. 4B, as anaxial cross-section, and FIG. 4C, as a diametric cross-section, havingthe patch areas 92 and 96 at circumferentially opposed locations. Itshould be understood the patch could also extend around the entirecircumference in some applications.

A method of repairing a composite material tube could be said to includethe steps of (a) identifying a damaged area on a composite tube; and (b)placing a patch(s) on a surface of the tube and over the damaged area.

When considering the drive shaft embodiments of FIGS. 2A-2C along withthe repaired shafts of FIGS. 4A and 4B, the term “ring” as utilized inthis application could extend generically to either thecircumferentially limited patches of FIGS. 4A and 4B or, of course, thefull circumferentially extending rings of FIGS. 2A-2C.

Although an embodiment of this invention has been disclosed, a worker ofordinary skill in this art would recognize that certain modificationswould come within the scope of this disclosure. For that reason, thefollowing claims should be studied to determine the true scope andcontent of this disclosure.

1. A method of repairing a composite material tube comprising the stepsof: (a) identifying a damaged area on a composite tube; and (b) placinga patch on a surface of the tube and over the damaged area.
 2. Themethod set forth in claim 1, wherein there are a plurality of patchlayers placed to cover the damaged area.
 3. The method set forth inclaim 2, wherein the patch is provided at an outer peripheral surface ofthe composite tube.
 4. The method as set forth in claim 3, wherein thecomposite tube is cylindrical, and the patch extends over a limitedcircumferential area of the composite tube.
 5. The method set forth inclaim 6, wherein at least a second patch is circumferentially spaced,but axially aligned with the patch over the damaged area, with alocation for the second patch being selected to provide balancing of thecomposite tube.
 6. The method as set forth in claim 5, wherein the firstand second patch are formed of polymer matrix material with reinforcingfibers.
 7. The method as set forth in claim 6, wherein the compositetube and the first and second patch are formed of the same compositematerial.
 8. The method as set forth in claim 4, wherein the compositetube and the patch are formed of a composite material.
 9. The method asset forth in claim 4, wherein the patch is formed of polymer matrixmaterial with reinforcing fibers.
 10. The method as set forth in claim4, wherein the composite tube and the patch are formed of the samecomposite material.
 11. The method as set forth in claim 4, wherein thecomposite tube is hollow.
 12. The method set forth in claim 1, whereinthe patch is provided at an outer peripheral surface of the compositetube.
 13. The method as set forth in claim 1, wherein the composite tubeis cylindrical, and the patch extends over a limited circumferentialarea of the composite tube.
 14. The method set forth in claim 13,wherein at least a second patch is circumferentially spaced, but axiallyaligned with the patch over the damaged area, with a location for thesecond patch being selected to provide balancing of the composite tube.15. The method as set forth in claim 14, wherein the first and secondpatch are formed of polymer matrix material with reinforcing fibers. 16.The method as set forth in claim 1, wherein the composite tube and thepatch are formed of a composite material.
 17. The method as set forth inclaim 16, wherein the patch is formed of polymer matrix material withreinforcing fibers.
 18. The method as set forth in claim 1, wherein thepatch is formed of polymer matrix material with reinforcing fibers. 19.The method as set forth in claim 1, wherein the composite tube and thepatch are formed of the same composite material.
 20. The method as setforth in claim 1, wherein the composite tube is hollow.